df.select(coalesce(col("Description"),col("CustomerId"))).show
spark.sql("select ifnull(null,'return_value'),nullif('value','value'),
nvl(null,'return_value'),nvl2('not_null','return_value','else_value')
from dfTable limit 1").show()
df.select(coalesce(col("Description"),col("CustomerId"))).show
spark.sql("select ifnull(null,'return_value'),nullif('value','value'),
nvl(null,'return_value'),nvl2('not_null','return_value','else_value')
from dfTable limit 1").show()